Why does rigidbody rotate randomly on its own?

I don’t know if this question is asking too much but I have a bike using sphere colliders on the wheels and a rigidbody for the parent object of the entire model.

My issue is that after the bike goes up any form of uneven terrain (ramps, small bumps, etc) it’ll just, at random, rotate up to 90 degrees and stay there. Sometimes it’ll rotate slightly (but not consistently the same angle) and eventually level back out. And it’s always rotating forwards up until that 90 degrees mark.

One last thing, is that when it launches off the ramps it’ll go up then start rotating forwards to face towards the ground. But again, its angle is always random. Does anyone have any idea WHY it’s doing this?

Swap the Spheres for wheel colliders and make sure the bike and the wheels are not able to collide with each other in the Collision Matrix